Along with the rapid distribution of information-related equipment and communication equipment such as personal computers, video cameras, and mobile telephones in recent years, development of batteries used as power supplies thereof has been considered important. Furthermore, even in the automotive industry and the like, development of high power output and high capacity batteries for electric vehicles or hybrid vehicles is in progress. Currently, among various batteries, more attention is paid to lithium batteries from the viewpoint of having a higher energy density.
Lithium batteries that are currently commercially available use liquid electrolytes containing flammable organic solvents, and therefore, installation of safety devices that suppress temperature increases at the time of short circuit, or a structure for preventing short circuit is needed. In this regard, it is believed that since a lithium battery that has been converted to an all solid state battery by changing the liquid electrolyte to a solid electrolyte layer, does not use a flammable organic solvent within the battery, simplification of the safety device can be attempted, and the battery is superior in terms of product cost or productivity.
Furthermore, in the field of lithium batteries, it is known that short circuit caused by dendrites occurs. A short circuit occurs when, at the time of charging, Li that has been precipitated in the anode active material layer grows in the direction of the cathode active material layer, and the anode active material layer and the cathode active material layer are physically brought into contact. In order to prevent short circuit, investigations have been conducted. For example, Patent Literature 1 discloses a method of producing a non-aqueous electrolyte battery, the method comprises a step of forming a first solid layer by heating a powder of an amorphous solid electrolyte; and a step of forming a second solid layer on the first solid layer by a gas phase method. On the other hand, Patent Literature 2 discloses a Li2S—P2S5—LiI-based sulfide solid electrolyte material.